The invention relates to new thienothiophene derviatives. The invention further relates to their use as semiconductors or charge transport materials, in optical, electrooptical or electronic devices like for example organic field effect transistors (FET or OFET) for thin film transistor liquid crystal displays and integrated circuit devices such as radio frequency identification (RFID) tags, electroluminescent devices in flat panel displays, and in photovoltaic and sensor devices. The invention further relates to a field effect transistor, light emitting device or identification (ID) tag comprising the new thienothiophene derivatives.
Organic materials have recently shown promise as the active layer in organic based thin film transistors and organic field effect transistors [see H. E. Katz, Z. Bao and S. L. Gilat, Acc. Chem. Res., 2001, 34, 5, 359]. Such devices have potential applications in smart cards, security tags and the switching element in flat panel displays. Organic materials are envisaged to have substantial cost advantages over their silicon analogues if they can be deposited from solution, as this enables a fast, large-area fabrication route.
The performance of the device is principally based upon the charge carrier mobility of the semiconducting material and the current on/off ratio, so the ideal semiconductor should have a low conductivity in the off state, combined with a high charge carrier mobility ( greater than 1xc3x9710xe2x88x923 cm2Vxe2x88x921sxe2x88x921). In addition, it is important that the semiconducting material is relatively stable to oxidation i.e. it has a high ionisation potential, as oxidation leads to reduced device performance.
Compounds known in prior art for use as semiconductors are the fused dimer of dithienothiophene (DTT) and xcex1,xcex1xe2x80x2-bis(dithieno[3,2-b:2xe2x80x2,3xe2x80x2-d]thiophene (BDT) having the structures shown below. 
BDT and DDT are described for example in F. de Jong and M. J. Janssen, J. Org. Chem., 1971,36,12, 1645; S. Inaoka and D. M. Collard, J. Mater. Chem., 1999, 9, 1719; H. Sirringhaus et al, Appl. Phys. Lett. 1997,71 (26), 3871; X-C. Li et al, J. Am. Chem. Soc., 1998,120, 2206, and in the international patent application WO 99/12989.
In particular BDT, which has been extensively studied, has been shown to be an effective p-type semiconductor for organic FETs with a very high charge carrier mobility of 0.02-0.05 cm2/V. BDT also has been found in the solid state to have a completely coplanar formation, and to be more planar than oligomers of thiophene.
However, the materials described in prior art have several disadvantages. BDT has a high melting point and is very insoluble, therefore, if used as the active layer in an organic thin film transistor, it cannot be readily solution processed.
As a result, for applications like FETs, prior art materials like BDT are usually deposited as a thin film by vacuum deposition, which is an expensive processing technique that is unsuitable for the fabrication of large-area films.
It was an aim of the present invention to provide new organic materials for use as semiconductors or charge transport materials, which are easy to synthesize, have high charge mobility, and good processibility. The materials should be easily processible to form thin and large-area films for use in semiconductor devices. Other aims of the invention are immediately evident to those skilled in the art from the following description.
It was found that these aims can be achieved by providing thienothiophenes as described below.
U.S. Pat. No. 4,639,328 discloses compounds with a thienothiophene group for use as components of liquid crystalline phases, but does not provide any suggestion to semiconductor materials.
Definition of Terms
The terms xe2x80x98liquid crystalline or mesogenic materialxe2x80x99 or xe2x80x98liquid crystalline or mesogenic compoundxe2x80x99 means materials or compounds comprising one or more rod-shaped, lath-shaped or disk-shaped mesogenic groups, i.e. groups with the ability to induce liquid crystal phase behaviour. The compounds or materials comprising mesogenic groups do not necessarily have to exhibit a liquid crystal phase themselves. It is also possible that they show liquid crystal phase behaviour only in mixtures with other compounds.
One object of the invention is to provide thienothiophene compounds of formula I
R1xe2x80x94Z1xe2x80x94(A1xe2x80x94Z2)mxe2x80x94(Txe2x80x94Z3)nxe2x80x94(A2xe2x80x94Z4)oxe2x80x94R2xe2x80x83xe2x80x83I
wherein
R1 and R2 are independently of each other H, halogen, CN, NO2, straight chain, branched or cyclic alkyl with 1 to 20 C-atoms, which may be unsubstituted, mono- or poly-substituted by F, Cl, Br, I or CN, it being also possible for one or more non-adjacent CH2 groups to be replaced, in each case independently from one another, by xe2x80x94Oxe2x80x94, xe2x80x94Sxe2x80x94, xe2x80x94NHxe2x80x94, xe2x80x94NR0xe2x80x94, xe2x80x94SiR0R00xe2x80x94, xe2x80x94COxe2x80x94, xe2x80x94COOxe2x80x94, xe2x80x94OCOxe2x80x94, xe2x80x94OCOxe2x80x94Oxe2x80x94, xe2x80x94Sxe2x80x94COxe2x80x94, xe2x80x94COxe2x80x94Sxe2x80x94, xe2x80x94CHxe2x95x90CHxe2x80x94 or xe2x80x94Cxe2x89xa1Cxe2x80x94 in such a manner that O and/or S atoms are not linked directly to one another,
R0 and R00 are independently of each other H or alkyl with 1 to 12 C-atoms,
A1 and A2 are independently of each other an alicyclic or aromatic group that may also comprise one or more hetero atoms and one or more fused rings, and A1 may also denote T,
Z1 to Z4 are independently of each other xe2x80x94Oxe2x80x94, xe2x80x94Sxe2x80x94, xe2x80x94COxe2x80x94, xe2x80x94COOxe2x80x94, xe2x80x94OCOxe2x80x94, xe2x80x94Oxe2x80x94COOxe2x80x94, xe2x80x94COxe2x80x94NR0xe2x80x94, xe2x80x94NR0xe2x80x94COxe2x80x94, xe2x80x94OCH2xe2x80x94, xe2x80x94CH2Oxe2x80x94, xe2x80x94SCH2xe2x80x94, xe2x80x94CH2Sxe2x80x94, xe2x80x94CF2Oxe2x80x94, xe2x80x94OCF2xe2x80x94, xe2x80x94CF2Sxe2x80x94, xe2x80x94SCF2xe2x80x94, xe2x80x94CH2CH2xe2x80x94, xe2x80x94CF2CH2xe2x80x94, xe2x80x94CH2CF2xe2x80x94, xe2x80x94CF2CF2xe2x80x94, xe2x80x94CHxe2x95x90Nxe2x80x94, xe2x80x94Nxe2x95x90CHxe2x80x94, xe2x80x94Nxe2x95x90Nxe2x80x94, xe2x80x94CHxe2x95x90CR0xe2x80x94, xe2x80x94CX1xe2x95x90CX2xe2x80x94, xe2x80x94Cxe2x89xa1Cxe2x80x94, xe2x80x94CHxe2x95x90CHxe2x80x94COOxe2x80x94, xe2x80x94OCOxe2x80x94CHxe2x95x90CHxe2x80x94 or a single bond,
X1 and X2 are independently of each other H, F, Cl or CN,
T is a group consisting of 3, 4, 5 or 6 thiophene rings which may also be mono- or polysubstituted by R1, wherein at least 3 of the thiopene rings are fused together,
m and o are independently of each other 0, 1, 2 or 3, and
n is 1, 2 or 3.
Another object of the invention is the use of compounds of formula I as semiconductors or charge transport materials, in particular in optical, electrooptical or electronic devices, like for example components of integrated circuitry, field effect transistors (FET) for example as thin film transistors in flat panel display applications or for Radio Frequency Identification (RFID) tags, or in semiconducting components for organic light emitting diode (OLED) applications such as electroluminescent displays or backlights of flat panel displays, for photovoltaic or sensor devices, as electrode materials in batteries, as photoconductors and for electrophotographic applications.
Another object of the invention is a field effect transistor, for example as a component of integrated circuitry, as a thin film transistor in flat panel display applications, or in an RFID tag, comprising one or more compounds of formula I.
Another object of the invention is a semiconducting component, for example in OLED applications like electroluminescent displays or backlights of flat panel displays, in photovoltaic or sensor devices, as electrode materials in batteries, as photoconductors and for electrophotographic applications, comprising one or more compounds of formula I.
Another object of the invention is a security marking or device comprising an RFID or ID tag or a FET according to the invention.
Upon further study of the specification and appended claims, further objects and advantages of this invention will become apparent to those skilled in the art.